1. Field of the Invention
The present invention relates to an electrophotographic copying apparatus. More particularly, the present invention relates to an electrophotographic copying apparatus capable of forming images in a color mode and in an outline image forming mode.
2. Description of the Prior Art
Recently, there have been proposed various electrophotographic copying apparatus capable of copying not only images in black but also images in red, blue and other colors. Such an apparatus usually comprises two kinds of developing devices between an exposure device and a transfer device. One of the developing devices is used as an ordinary developing device having developer containing black toner and the other developing device is used as a color developing device having developer containing color toner. Thus, either of the developing devices is selectively operated.
Generally speaking, the peripheral outline of an image is in practice full of necessary information thereabout and represents sufficiently the characterizing features of the given image, thus playing among others a most important role in the judgment of the latter. The so-called outline image forming means is adapted such that a peripheral outline is picked up from a generally full and positive documentary image and is devoid of intermediate tones or reversely, solid representations, thus being most effective for the identification of the practical image and for pattern recognition purpose thereof.
For example, complex color image patterns can be obtained by such an apparatus in a manner of forming by execution of successive copying operations a blank pattern encircled by a color outline or preparing a blank pattern for later producing differently colored local image areas contained therein.